This study investigates how far mitochondrial swelling in the ischemic heart is influenced by factors pertaining to anaerobic energy turnover. Canine hearts were arrested by aortic cross clamping or cardioplegically with St. Thomas or
HTK solution and incubated at 25 degrees C in the
solution used for
cardiac arrest. Samples of the left ventricle were taken at the end of
cardiac arrest and during
ischemia for structural evaluation and biochemical analysis. The extracellular pH in the interventricular septum was measured. Mitochondrial swelling was determined with the surface to volume ratio, a parameter independent of the reference space. Values obtained for different swelling were related to defined metabolite concentrations and pHe values to establish possible correlations between structural and biochemical parameters in the ischemic heart. At the onset of
ischemia and during the breakdown of
creatine phosphate (CP) to 3 mumol/g wet weight mitochondrial volume depends on the method of
cardiac arrest and does not increase significantly in any of the three groups. The degree of mitochondrial swelling after depletion of CP correlates with the decline in
ATP independent of the form of
cardiac arrest. Characteristic values of the surface to volume ratio ascertained at different times of
ischemia for all groups correspond to determined
ATP concentrations.
Acid pHe values seem to intensify mitochondrial swelling. With increased
lactate concentrations mitochondria swell, but first initially the degree of swelling differs significantly in the forms of
cardiac arrest investigated. Thus, the surface to volume ratio is a powerful and valid ultrastructural parameter, which makes correlations between mitochondrial structure and metabolism possible and furthermore indicates a strong correlation between mitochondrial swelling and
ATP-concentration in the ischemic heart.